People get themselves into dangerous situations all the time. Whether you're one of those people or you just happen to travel with them, having an app like 1st Response: Emergency Kit could be a life saver. This app gives you detailed information on things ranging from first aid to survival, offers a distress signal, lights, a private profile, and even the ability to call emergency contacts.
The resources section provides advanced information on preparation, first aid, road side repair,survival, and other. The distress tab allows you to set an SOS in multiple different colors and frequencies so that you can be seen. You'll get the best visibility by turning your brightness to the max in settings. You can also use the light feature to help see in the dark or check someones pupils as there are so many different ways to customize how it is shown.
The profile is pretty interesting as well. This is where you would fill out all of your information before you decide to go on any crazy adventure with your iPhone. You can put your picture, list any medical alerts, your medications that you're taking, emergency contacts, and then basically fill out an extensive health history survey. This could be really useful if you happen to get hurt with your iPhone on you and the person actually checks this app.
Having this app to help others is a great idea. Having it to help yourself is less useful as unless you tell someone to specifically look for it on your phone, they aren't going to wonder if you have this app installed. Chances are, if you can tell them to look on the phone for the app, you can answer the questions they'll have for you.